Field of the Invention
The present invention relates to a slip ring apparatus for an electric rotating machine such as an alternator for the vehicle.
Description of the Background Art
An electric rotating machine, such as an alternator for the vehicle, uses a slip ring apparatus in which a pair of slip rings each having a lead joined thereto are integrally formed by a molded body made of an insulating resin. Conventional slip ring apparatuses sometimes cause defects due to displacement or deformation of the leads, which result from the pressure of the resin during insert molding, and a structure which prevents these defects has been required.
For example, Patent Document 1 proposes, as a configuration for absorbing the deformation of the leads and allowing the lead to be disposed at a predetermined position, provision of a deformation absorbing portion in the lead within a connecting portion that connects a slip ring support cylindrical portion and a terminal retaining portion to each other. The deformation absorbing portion is such that the strength of the lead is lowered locally to absorb the deformation of the lead at the time of insert molding. This conventional Document mentions, as the examples of the deformation absorbing portion, a bend portion in which the lead is bent in a substantially V shape or in a substantially U shape, a cut-out portion in which the lead is cut out to be formed to have a smaller thickness, and a through-hole portion that intersects with a shaft.
In Patent Document 2, in order to avoid contact between a slip ring support cylindrical portion and a coil connection terminal, an insert is disposed at a linear portion between the slip ring support cylindrical portion and the coil connection terminal to ensure a sufficient gap. Patent Document 3 proposes a slip ring apparatus having through-holes for positioning the leads before insert molding in order to properly set the interval distance along the radial direction.
[Patent Document 1] Japanese Patent No. 3812456
[Patent Document 2] French Patent No. 2928043 B
[Patent Document 3] Japanese Patent No. 3622118
The technique of providing the deformation absorbing portion, which is proposed in Patent Document 1, has the following problems. In the case that the deformation absorbing portion is a bend portion, there is a possibility that the thickness of the bend portion that has been deformed does not fall within the range of the thickness of the connecting portion because the connecting portion, in which the lead is buried, does not have a sufficient radial thickness size. In the case that the deformation absorbing portion is a cut-out portion or a through-hole portion, the thickness of the lead does not increase, but it is possible that the lead may not fit into the insulating member because of deformation. In either case, there is a risk that the lead may be exposed outside the insulating member depending on the degree of deformation of the deformation absorbing portion.
In addition, in the case that the deformation absorbing portion is a cut-out portion or a through-hole portion, the strength of the lead is lowered locally at that portion. Consequently, there is a possibility that the lead cannot be able to withstand external forces and may result in breakage. In the slip ring apparatus, it is impossible to confirm in what shape the lead is accommodated in the molded body. Moreover, the slip ring apparatus is used for a long term in a vehicle. For these reasons, it is undesirable, from the viewpoint of reliability, to lower the strength of the lead by providing the deformation absorbing portion in the slip ring apparatus.
Although the technique proposed in Patent Document 2, in which the insert is disposed at the linear portion, appears to be able to determine the position of the lead at the time of secondary molding. However, strictly speaking, the technique can restrict the position of the lead only in radial directions. In the technique proposed in Patent Document 3, in which the positioning of the lead is carried out by a through-hole, the linear portion of the lead is not retained. For this reason, the bent portion of the lead may be displaced because of the pressure of the resin at the time of molding.